The present invention relates to a working cylinder with dampened ends, which may be deployed in the areas of fluid technology where the ends require dampening.
Systems are known where the suppressing of the main piston of a working cylinder at each stroke end is performed by a reduction of the flow cross section area for the outlet fluid power, complemented in many cases by a pressure regulating valve which can externally set. In terms of construction a very wide range of designs exists. They can be divided into systems which display the throttled outlet cross section as stationary parts of the working cylinders, or systems where the dampening throttle is incorporated in the moving parts of the cylinder. The basic function of the dampening is aimed at decelerating the total kinetic energy of the moving parts of the cylinder for keeping the impact energy as low as each individual application allows. The function of a cross section reduction in the course of the movement of the piston towards the end--from the time when the dampening commences--determines piston towards the ends--from the time when the dampening commences--determines the dampening characteristics. There are known dampening systems which abruptly seal off the discharge cross section and conduct the flow via the throttle cross section or systems where the dampening is performed progressively in the sense of a gradual adjustment to the resting state of the piston, whereby the throttle cross section is gradually reduced in the course of the piston movement.
This is supported by some publications. The publication DE-OS 1925166 refers in its description on the state of art to the publication DE-AS 1256296 where a special dampening element is described whereby publication DE-AS 1246296 where a special dampening element is described whereby the piston pushes the pressure medium through a narrow gap and acts as a pressure controlled dampener on the piston.
There is also a description of a check valve in the piston as well as check valves in the small cross section outlets in the cylinder barrel wall over a part which is passed by the piston. In doing so a special, locally controlled contour function is implemented in such a manner that the cross section of the outlet is ideally proportionate to the square of the stroke.
Publication DE-G 6943765 describes an outlet for the pressure medium in front of the cylinder end for dampening purposes, in which the outlet leads into the inlet supply line of the working cylinder. An annular gap which is created by an undersized ring with a gap between it and the cylinder acts as a pressure controlled dampening element. Additionally, there is an annular grove in the piston as well as a check valve between the annular groove and the cylinder chamber within the piston for directional control.
In publication DE-OS 2206410 a dampening via a throttle valve in the pressure medium outlet is described, into which an extension of the piston is extended, as well as a check valve in the piston itself. In accordance with the invention the dampening is achieved here through a special shape of piston whereby an undersized ring with accessible space forms a common space with the cylinder. The outlet pressure medium from the latter is throttled and the dampening cross section corresponds to the piston cross section.
Publication U.S. Pat. No. 4,207,800 achieves dampening with the help of a special piston ring which sits at the end of the piston, has some axial movement and is somewhat undersized, whereby ac heck valve is formed by the unilaterally broken surface of the ring and by compressing of the pressure medium in the cylinder chamber a pressure controlled dampening by means of the annular gap is achieved.
An equally simple dampening is described in the publication U.S. Pat. No. 4,425,836. Here the dampening is achieved through an annular groove located between the piston and the cylinder. In this way it is a functional of the dampening as the effective spiral extends as the piston approaches the end.
Publication DE -G 9418042.3 describes a remnant cylinder space as a dampening component by means of a secondary pressure medium cylinder which functions directly as a damper. Superimposed on this a pressure controlled dampening takes place by means of the annular gap incorporated into the undersized piston ring, as well as a position controlled dampening via the effective length of the spiral groove which increases towards its end. In this case the spiral groove is positioned in the stroke area of the piston ring.
The drawback in all the described variations is the high level of constructive expenditure on achieving a deceleration of the moving masses without an impact. No simple construction for adjusting the appropriate dampening to the concrete application is available.
Traditionally, the dampening follows the function: EQU P.sub.2 .times.z.gtoreq.W.sub.k .+-.W.sub.p
wherein:
P.sub.2 =dampening pressure, Z=cylinder constant, W.sub.k =kinetic energy, W.sub.d =pressure energy of the dampening distance, W.sub.p =potential energy of the position.
In order to achieve the desired dampening effect--while simultaneously maintaining the required operating power--p.sub.2 must be increased.
This takes place via:
a) by increasing of the operating pressure, since then p.sub.2 as the dampening dynamic pressure can be increased evenly. or PA1 b) by enlarging the working cylinder, since the dynamic pressure of the throttle can be increased.
Both versions are inefficient in terms of energy and in the case of a sudden reduction of the cross section can create a hazard by a oscillating deceleration of the masses. These dampening variations warrant no timing related positioning of the dampening. In aiming at a progressive dampening the high level of constructive expenditure dominates and becomes often commercially unviable.